/Engine/Source/Editor/SceneOutliner/Public/ISceneOutlinerMode.h
Select all descendants of a folder. Optionally select only immediate descendants.
virtual void SelectFoldersDescendants ( const [TArray](API\Runtime\Core\Containers\TArray)< [FFolderTreeItem](API\Editor\SceneOutliner\FFolderTreeItem) * > & FolderItems, bool bSelectImmediateChildrenOnly )